Headgear of Mystery

Highly appreciated by fans of investigations, puzzles and other disciplines that lead to headaches, this headgear has its own mystery, which has not been solved to this day: why do those who wear it grow a magnificent moustache when they equip it? The most-accepted theory (but not necessarily the most correct one) is that no one can solve an investigation without a big moustache. (Place this headgear over other, already-equipped headgear to change its appearance.)